How to provide reliable mobile wireless transmission of video, data, and speech at high rates to many users has been intensively studied in recent years.
One known system and method for improving video transmission over a wireless network is disclosed in PCT application number PCT/EP01/01878 (publication number WO 01/65848, referred hereafter as D1). As disclosed, D1 is tailored to solve video transmission problems in RF band and the system proposed is limited to single antenna system.
Michael B. Pursley developed one approach using nonuniform M-ary Phase-Shift-Key (M-PSK) constellation in multicast transmission of multimedia message to receivers of different capabilities (Michael B. Pursley, John M. Shea, “Nonuniform Phase-Shift-Key Modulation for Multimedia Multicast Transmission in Mobile Wireless Networks,” IEEE Journal on Selected Area in Communications, VOL. 17, No. 5, May 1999). The system is based on one transmitter antenna and one receiver antenna. So its spectral efficiency and performance are limited.
Erik G. Larsson proposed a new differential space-time codes tailored to point-to-multipoint, or broadcast, communications using layered source coding (Erick G. Larrson, “Nonuniform Unitary Space-time Codes for Layered Source Coding,” IEEE Trans. On Wireless Communications, VOL. 3, No. 3, May 2004). The transmission of an additional message incurs performance degradation and the selection of signal constellation is limited.
One known way to get high rates on a wireless wideband channel is to use multiple transmitter and/or receiver antennas. Multiple Input Multiple Output (MIMO) technology significantly enhances system performance. Using proper space-time coding, it is possible to use the degrees of freedom of the MIMO channel both to increase the throughput and to counteract fading. Space-time coding and modulation strategies have recently been adopted in 3G cellular standards (e.g., CDMA2000 and WCDMA) and have also been proposed for wireless local loop (Lucent's BLAST project) and wide-area packet data access (AT&T's Advanced Cellular Internet Service). However, multiple antenna deployment requires multiple RF chains.
Another fact should be noted that distinct receivers have different capabilities of decoding a message, which suggests that the transmitted signal should consist of several components which are of different importance for the reconstruction of the message. Then came the concept of layered source coding and multilevel-modulation. Layered source coding is now a mature technique employed in many multimedia standards. For instance, the image-coding standard JPEG-2000 and the video coding standard MEPG-4 what is sometimes referred to as “fine granularity scalability,” which enables a gradual tradeoff between the error-free data throughput and the quality of the reconstructed image or video sequence. Such progressive source coding methods are already in use in many Internet applications where data rate can be traded for quality, and they are expected to play an instrumental role for the next generation of wireless standards to provide ubiquitous access both to the Internet, and to diverse sources of streaming video and audio. It is envisioned that in some existing applications, the basic message may be a voice message or a control message that must be delivered to several radios.
There remains a need for exploiting the additional capacity of some of the links to deliver data simultaneously to the more capable receivers with higher complexity. Namely, the more-capable radios in a store-and-forward network could be used to advance a data packet toward its destination while they are also handling voice messages, or a voice packet can be forwarded to a more-capable radio at the same time that a network control packet is being sent.
Therefore, there is a need in the art for improved system and method for use not only in RF band but more advantageous in base band, also a further need for improved system and method that can adopt both coherent receiver and non-coherent receiver.
In these situations, it could be understood that fading conditions change so rapidly that channel estimation is difficult or require too many training symbols. Therefore, it is desirable to avoid channel estimation in order to reduce the cost and complexity of the handset.
It is further desirable to develop new wireless communication methods that achieve a higher spectral efficiency (data rate per unit bandwidth) and deliver image efficiently for a given power expenditure.